Piston



June 2 5, 1929. J. w. 'McQUAlD 1,718,474

rIs'roN- Fil Aut 9. 192e 'Patented .im 2s, D192e.

",UNITED STATES JOHN W. MQQUAIID, F FILLHOBE, CALIFOBIA.

r'IsToN.

Appuemon' akakaugut s, 192s. semi No. masa.

My invention relates to pistons, applicable alike to single or double acting pumps or en ines, although in its preferred specific emodiment, it is most efficient in double acting pumps.

In the conception and perfecting of this invention I have had in mind the inherent defects and shortcomings of metallic pistons and rings, when used for pumping fluids havving a considerable content of abrasives such as sand or silt. Due to their unyielding qualities this solid matter causes rapid attrition of their peripheries, and as there is a tendencyto concentratev wear when once started, these soon i lose their efficiency. I have alsblhad in. mind the deficiencies of the usual type of flush pump piston wherein an expansible packing is used and which requires frequent adjust-.

ments during operation, to maintain its efficiency. As such adjustments are usually not made until wear takes place, considerable irremedial damage and premature wear always 'results from use.

Y Considering these matters, I have provided a piston formed' of a yielding material, having no rings, in which the sealing is effected by the inherent yielding characteristics of the material of which it is formed and whichl v not 'only resists rapid wear, caused by solid matter, but also compensates for peripheral wear, whether concentrated or otherwise.

I I am aware that pistons have been heretofore produced, having yielding or flexible cylinder engaging packing members, so arranged that the internal fluid pressure of the cylinder operates to effect sealing action, but

those differ radically from the principles embodied in my invention. In such cases the lpacking is rawn away from the cylinder Walls, by suction, on the intake stroke'and on the wor stroke the piston must travel some distance before sufficient pressure is built up to again effect its sealing expansion. During this time the contained abrasives work between the packing and cylinder wall and then when the fluid pressure becomes sufciently great to effect the sealing action, cutting or abrading of the piston and cylinder walls takes place and considerable damage is-done 50, before the abrasives can be removed. With my improved type of piston, dile to the in. herent yielding characteristics of the rubber packing member, andthe particular manner o fmigts formation, there is a constant yielding presslal contact with the cyhnder wall, ir-

/a lar er normal diameter sure is develo respective of the extent of fiuidipressure in the cylinder. Additionally, dueto the peripheral ends -of the packing'meinber being of l cylin er, whenunconfined therein, contact is always maintained and wear automatically compensated for, withdrawal of these ends from the cylinder wall, on theu suction stroke, 1s resisted, and there is immediately a close Vpressural Contact between these ends and the cylinder wall at the beginnin of the work A stroke, thereby preventing a rasives from working between the packing member and cylinder-wall, even before sufficient fluid presed in the cylinder to effect such action, as in t e case of other types of pist'ons.

.It is also a feature of my piston that its sealing action isA superinduced by the fluid pressure in the cylinder so that 1t is proportional to the pressure created, and in the accomplishment of this end its fiexible portion is formed in the manner and described.

Another feature of my piston is that, while the sealing is effected on the work end, during the pressure stroke, Ifrictional engagement of the opposite or trailing end with the cylinder wall-not being y subjected to pressureis minimized not only -reducin power loss (due to friction) to a lminimumnut also permitting the escape of any silt or sand from be-v than that of the.

configuration-hereinafter field andconduces to economy in well pumps Where the fiuid carries an appreciable portion of detritus. y

The salient features of my invention are more fully set forth in thefollowing specificat'ion, reference -being made therein tc the accompanying'- drawings, forming a part hereof.Y In these drawings llhave illustrated the preferred 'specific embodiment of my invention,designed primarily for use in double acting pumps; the several views being described as follows:

Fig. 1 is a fragmentary, longitudinal sectional view throughv a typical cylinder showing my piston therein;

Fig. 2 is a similar view of my piston removed.- fromthe cylinder;

Fig. 3 is aside elevation of the piston core;

Fig. 4-is an end View thereof; and f Fig. 5 is a diagrammatic view, illustrating the action of the fluid pressure in the cylinder upon the piston.l

While I will hereinafter describe the details of construction and operation ofthe preferred specific embodiment of my piston, in order that the principles of my invention may be fully understood by those skilled in the art, it is nevertheless to be understood that I reserve the right'to make such changes or modifications in structure and arrangement as will properly come within the scope of the appended claims, when construed in the light of the doctrine of equivalents.

In the drawings the numerallO designates a typical engine or pump cylinder; and inasmuch as I contemplate my` improvement having its widest and most practical application in pumps, I will hereinafter consider it as used in this connection, primarily for the purpose of clearly disclosing its principles of operation.

The piston rod 12 maybe connected to the hub or nave 11 by. any suitable means and for purposes of illustration I have shown this to be a screw threaded connection.

The nave 11 is preferably cylindrical, extending longitudinally throughout the length of the yielding portion 13,-and has a single, large, radially extending peripheral flange 14, substantially midway of its length, extending into the yielding packing portion 13. While any number of flanges 14, of different sizes, may be provided on the nave 11, for all purposes of this description one will suffice. The surface of the nave 11, as well as the faces -of the flange 14 may be provided with alternate ribs or flanges 15 and grooves 16, spaced from each other in the manner illustrated. Those on the core 11 may be peripheral, as illustrated in Fig. 3, and those upon the lateral faces of the flange 14 may be concentric,

as illustrated in Fig. y4.- When the depths of the ribs 15 are increased 'the intermediate grooves 16 may be eliminated.

While the flange 14 is provided for the purpose of' laterally and longitudinally reinforcing thelyielding portion 1 3, as well as holding it against axial' movement upon the nave 11,

the ribs or flangesl and grooves 16 are proy vided to additionally retain the yielding portion both against axial movement on the nave and transverse movement away from 1t, 1ndv termediate its ends; As will be hereinafter explained one of the particularfeatures of the invention is `the supporting'of the yielding portion 13 in such a manner that its ends 13 will have a certain freedom of movement or lateral flexibility. Thus the essential thing is to so support this yielding portion upon the nave so that while there will be a slightylateral yielding action opposite the periphery of the flange 14, along the line A-A, this portion of the piston will be comparatively rigid and the portions adjacent the ends 13a more flexible. For this reason the ribs or flanges 15 and grooves 16 are provided to prevent any relative movement bethe nave 11 so that it will extend into the grooves 16 and so the ribs or flanges 15 will extendjinto it, in the manner illustrated. While ribs or flanges 15 and grooves 16 are provided'for the purpose 'speciedit is to be understood that an equivalent means for holding the rubber portion 13 against movement relative to the nave 11, may be used. However, the method 'shown has been found, so far, to be the most practical and advisable for the purpose.

The ends of the rubber portion 13 are annularly recessed, as at 19, and while these recesses may be of a uniform depression or concavity, of any required depth, it is preferred that they'be -`formed in the manner illustrated to provide the longitudinally overhanging peripheral ends 13a. That is, instead of the surface of the concavities 19 forming a juncture With the peri hery 18 at a more or less acute angle, these aces may be formed in reverse or ogee curvatures eX- tending from the body portion to the periphery 18l with the rounded, built up portions Q0 forming a juncture with the periphery 18l at an angle ,of about or a little less than degrees. Thus when the piston' is within the cylinder, as illustrated in Fig. 1, this additional material at` the ends will reinforce them from the body portion and not only resist Wear but will also give such rigidity as to insure a close frictional contact with the cylinder wall and thus minimize' the passage of sand and-silt past the piston ends.

In forming the rubber portion 13 it is also preferred' that its periphery 18 be made concave, or its central portion made of a smaller diameter than the ends, as illustrated in Fig. 2, to also insure as close .frictional engagement of the ends 13a with the cylinder wall as is consistent with the -work to be done.

In Fig. 5 I have illustrated diagrammatically the-action Vof the,fluid pressure in the cylinder upon the piston to augment lits sealing action. vIn producingthis piston it will, of course, be made slightly larger than the bore of the cylinder, as illustratedv byy dot dash lines in Fig. 2, so that the yielding material will be slightly compressed when inserted therein, thus insuring a closey sealing Contact between it and the cylinder wall, due to the'inhercnt yielding qualities O the ma1 of the periphery 18 the ends 13 will be larger arrows, thus augmenting the natural sealing.

in diameter than 'along the portion A--A F ig. 2) so there will be a little greater pressurable contact with the cylinder wall at these ends.

In Fig. 5 the piston is shown moving upon its work stroke, and considering this to be a double acting pump, the pressure created in the chamber B will act against the concave face of the piston end, as illustrated by the action of. the yielding portion; and just in proportion to the increase in pressure produced in the chamber B will the end 13* be forced to more closely engage the cylinder wall. The chamber C, being the suct1on end on this stroke is under partial vacuum, which has a tendency to draw 'these ends away from the cyllnder wall, as illustrated by the arrows; thereby permitting the free escape of sand from between the periphery 18 at this end and the cylinder wall, as well as reducing to a minimum loss of power due to friction.

-In a double acting pump these operations are, of course, reversed upon each work stroke. With this construction the maj or portion of. the sealing is effected at the end 13' in 'the chamber under compression while the oppositeefect-is produced at the opposite end. v

While I have illustrated and described a i piston applicable -to a double actin pump arrangement, it is, of course, to be un erstood that its principles may be embodied in a sin- 'gle act-ing pump orengine and its construction altered to suit these tions.

Having described a invention, I claim:

1. Apiston comprising a relatively rigid axial'core; a relatively rigid radial flange von the core, the lateral faces of the flange being recessed; and a rubber packing member molded on said core and flange and extending particular condipreferred form of my intov the flange' recesses.

2. A piston comprising a relatively rigid` axialA core; a relatively rigid radial flange on the core, the lateral faces of the flange being annularly recessed; and a rubber packing member molded on saidv core and flange and extending into the flange recesses. p

3. A piston comprising a relatively rigid axial core; a relatively rigid radial flange o n the core; a plurality ofj concentric ribs on the lateral faces of the flange; and a rubber packingmember molded on the core and flange and extending into the annular spaces between said ribs.

'4. A piston comprising a-relatvely rigid axial core; arela'tively rigid radial flange on the core; the periphery of the core beingrecessed; and a rubber packing member molded on the core and flange andcxtending into the COre recesses.

lateral faces of the flange being recessed; and

a' rubber packing member molded on the core and flange and extending into the recesses therein.

7. A piston having a relativel rigid axial f core; a relatively rigid radial ange on the core; la plurality of relatively rigid concentric ribs on the lateral faces of the flange and a plurality of relatively `rigid circumferential ribs on 'the core; and a rubber packing member molded on the core, encasing the core, flange and the ribs thereon.

`8. A piston having a relativel rigid axial core; a relatively lrigid radial flange on the core intermediate its ends, tl1e lateral faces ofthe flange being recessed; a rubber packing member molded on the core, encasing the flange and extending into the flange recesses; the periphery of the packing member being substantially concave; and longitudinally overhanging peripheral end` portions on the packing member.

.9. A piston having a relativel rigid axial core; a relatively rigid radialfiange on the core intermediate its ends; a plurality of pe` ripheral recesses in the core; a rubber packing member' molded on the core, flangeand extending into the the periphery of the packing substantially concave; and overhanging peripheral ends member. Y 10. A piston havinga relatively rigid axial core; a relatively `.rigiil radial flange on the core intermediate its ends; the lateral faces of the flange being recessed and peripheral' recesses in the core; a rubber packing member molded on the core, encasing the flange and extending into the flange and core recesses.

A piston having a relatively rigid axial core ;\`a relatively rigid radial flange on the core recesses; member being longitudinally on the packing centric ribs onvthe lateral faces of the flange; a plurality of circumferential ribs on the core; a rubber packing member molded'on the core, encasing the flange,

the recesses between the flange and core ribs,

encasing the andextending into l,coreintermediate its ends; a plurality of conthe periphery of the packing member being I and longitudinally end portions o'n the axial core; a relativelyv rigid radial "flange on the'core intermediate its ends, the lateral faces of the flange. being recessed; a -rubf the cylinder wall when confined therein;

ber packing member molded on the core, encasing the flange and extending into the flange recesses; said packing member having a substantially concave periphery and longitudinally overhanging peripheral Iends, the end faces having an ogee curvature adjacent said overhanging peripheral ends.

13. vA piston comprising a relatively rigid axial core; a relatively rigid radial Hange on the core intermediate its ends; peripheral recesses in the core; a rubber packing member molded on the core, encasing the flange and extending into the said peripheral recesses; said packing member having a substantially concave periphery and longitudinally overhanging peripheral ends; the end faces having a-n ogee curvature adjacent said overhanging peripheral ends.

14. A piston comprising a relatively rigid axial core; a relativelyA rigid radial flange on the core intermediate its ends; the lateral faces of the flange and the` periphery of the i 'H--.QQEQll/ingirecessed ,"a-rubberrpacking niember .molded on the core, encasing the flange and extending into said recesses; said packing member having a .substantially concave periphery and longitudinally. overhanging peripheral ends, thel end faces having an ogee curvature adjacent said overhanging peripheral ends. l

15. A piston adapted for reciprocation in the bore of a cylinder, comprising a solid rubber packing sleeve, forming the'sole cylinder engaging element of the piston; a relatively rigid axial core extending through and radially reinforcing said sleeve throu hout its length; a relatively rigid radial ange on said core intermediate its ends, encased by the packing sleeve; longitudinally overhanging peripheral ends on the packing sleeve, said lends being of larger diameter than the cylinder bore whenunconfined therein, and the peripheral surface of the packing sleeve being formed to make unbroken contact with the cylinder lWall when confined therein. A

16. A piston adapted for reciprocation in the bore of a cylinder, comprising a vsolid rubber packing sleeve forming the sole cylinder engaging element of the piston; a relatively rigid axial core extending through and radially reinforcing said sleeve throughouty its length; longitudinally overhanging peripheral ends on the packing sleeve, said ends being of larger diameter than the cylinder bore when unconfined therein means i'n connection with vthe core to hold said sleeve against longitudinalv displacement' thereon, lsaid means being adaptedto permit radial flexing of the overhanging ends; andthe .peripheral surfacevof the packing sleeve being formed to make unbroken contact wlth e. 17! A piston adapted for reciprocation in the bore of'a cylinder, comprising a relativel rigid axial core; a relatively rigid radialy ange on the core intermediate its ends, said flange being of less diameter than that of the cylinder bore; a rubber packing sleeve formed on the core and encasing the flange; longitudinally overhanging 'peripheral ends on the packing sleeve, said ends being of greater outside diameter than that of the cylinder bore when unconfined therein, forming a peripheral-surface on the sleeve of less diameter intermediate its ends than at said ends, and said surface being formed to make unbroken contact With the cylinder wall when confined therein. 18. A piston adapted for reciprocation in the y'bore of a cylinder, comprising a relatively rigid axial core; a relatively rigid radial flangeonthe core intermediate its endsl/ said flange being of less diameter than the cylinder bbore; a radially resilient packing sleeve formed on theocore and encasing the flange, Awhereby said flange provides rigid radialbaEkngVforThecentral-portionYof the sleeve and rigid longitudinal backing`for" those portions-of the sleeve lying on either side thereof; said sleeve having radially extending end vfaces merging into longitudinally overhanging'peripheral endsfwliereby the internal'fluid pressure ofthe cylinder'on the Work stroke of the piston Will forge the overhangingf ends1 into close peripheral Contact withthe cylinder wall and by compression against the peripheral flange expand'the intermediate portion" of theV sleeve into close peripheral contact vith the. cylinder Wall.

19. A piston adapted for reciprocation in the bore of a' cylinder, comprising a relatively rigid axial core; a Arelatively rigid radial flange on the core intermediate its ends, said flange being of less diameter than the cylinder bore;4 a radially resilient packing sleeve formed on the core and encasing the flange, whereby said flange provides rigid radial backing for the central portion Aof the sleeve and rigid longitudinal backing for those portions of the sleeve lying on either side thereof; said .sleeve having radially extending end faces merging into overhanging peripheral ends, Wherebythe internal fluid pressure of the -cylinder on the work stroke of the piston will forcel the, overhanging ends into close peripheral contact With the cylinder walland by compression against theperipheral flange expand the intermediate portions of the sleeve into close peripheral Contact with the cylinder Wall; the overhanging peripheral ends being of greater-outside diameteig f flange on the core intermediate its ends, said flange being of less diameter `than the cylinder bore; a radially'resilient packingsleeve into close ends than at saidl formed on the core and encasing the fiange, whereby said flange provides rigid radial backing for the central portion of the sleeve and rigidjlongitudinal'backing for those portions of the sleeve lying on either side thereof;

said sleeve having radially extending end faces merging into overhanging peripheral ends, whereby the internal fluid pressure of the cylinder on the work stroke of the piston will force the overhanging ends into close peripheral Contact with the cylinder wall and by compression against the peripheral flange expand the intermediate portions of the sleeve peripheral contact with the cylinder wall ;y tlieperip'hery of the packing sleeve being of smaller ends, and having a surface adapted to make unbroken contact with the cylinder wall when confined therein.

21. A piston adapted for reciprocation in the bore of a cylinder, comprising a relativel? rigid axial core; a relatively rigid radial ange on the `core intermediate its ends, said flange being of lessl diameter than the cylinl tendin der bore.; a rubber packing sleeve formed on the core and encasing the flange, whereby said flange provides rigid radial backing for the central pJortion of the-sleeve and rigid longitudinal acking for those portions of the sleeve lying on either side thereof; said sleeve havin a concavel periphery and radially exend faces merging into longitudinally y overhanging peripheral end portions, whereby the said peripheral end portions are always maintained in close peripheral Contact with the cylinder wall when confined therein and whereby the internal fluid pressure of the cylinder on the work stroke of the piston will force the overhanging ends into closer peripheral contact with the cylinder wall and piind the 'interme iate portions of 4the sleeve into close peripheral contact with the cylinder wall.

' 22. A piston adapted for reciprocation in the bore of a cylinder, embodying a relatively rigid axial core.; relatively rigid radial reindiameter than the cylin said ends and the cylinder wall and whereby` herent ielding qualities of lypressural contact at all times between a radia radial constriction thereof is resisted.

' 23. A'piston adapted 'for reciprocation in the bore of a cylin er, .comprising a rubber packing sleeve; a lrelatively rigid axial core radially reinforcing said sleeve `throughout its length; said sleeve having a radiallyexdiameter intermediate its vh with theA` cylinder wall compression against the radial flangefexing ends on the' packingV of greater outside er bore when unconthe bodyv portion beneath`their`- outermost peripheral edges,

Vtermediateits' ends;'a solid rubber encas'ig the e make unbioken contact with the cylinder wall when confined therein; and relatively ,rigid radially extending reinforcing means in connection with the core, providing rigid longitudinal backing for. the sleeve, whereby the internal fluid ressure of the cylinder, on the work stroke o the piston, will force the overtact with the cylinder wall an sion against the radial reinforcing means will expand the intermediate portion into close peripheral contact with the cylinder wall.

24. A piston adapted for reciprocation through the bore of a cylinder, embodying a relatively rigid axial core; relatively rigid reinforcing means extending radially from said core and spaced from the work end thereof, said means bein of lesser radius than the radius of the cylin er bore; a rubber packing sleeve formed on the core, encasing said rein- 4 forcing means, the peripheral portion of the sleeve overhanging the bod portion at the work end, said end being of7 greater outside diameter than the c linder bore when unconfned therein, an said end bein annularly built up from the bod portion eneath its outermost peripheral edge whereby, due to the inherent yielding qualities of the sleeve, said end is constantly radially exfsf tending surface o n its work end, adapted to be the fluid pressure in the cylinanging end portion into close ressural con# .4 v

by compresioo panded -into tight peripheral en agement and where constriction thereof is resisted.

25. A piston embodying a relatively rigid axial core, radial reinforcing means on sa'fd core; a` solid rubber acking sleeve encasy radial :ing said core and rein orcing means and arranged. for unbroken pressural contact with a cylinder wall; longitudinally overhanging ends on the sleeve, said ends being of greater outside diameter than the cylinder bore when unconfined therein, and being annularly built up beneath,theiroutermost peripheral edges, whereby said overhanging ends are radially reinforced andsupported from the body porltion and whereby the inherent yielding qualities of the vsleeve insure "a constant radial pressural contact atall timesbetween said ends. and-the cylinderw'all and radial constriction isthereby resisted.

"26S-A piston-'embod ing :a relatively rigid axial i'core; a. radial ange on the core 1n.- king sleeve moldedvonto said core, core and flange, and being contrminous with the core, whereby the sleeve is axially reinforced throughout its length' by the core andV held'i against "axial displacement thereon by the Hange, said sleeve having a peripheral surface arranged for unbroken contact with the cylinder wall; the peripheral prtions of the ends of the sleeve overhanging the body portion thereofsaid ends also being of greater outside diameter than the cylinder bore when unconfinedtherein and being annularly built up from the body portion beneath and to the outermost peripheral edges, dially reinforced and supported from the body portion and whereby the inherent yielding qualities of the sleeve insure a constant radial pressu'ral contact at all times between said ends and the cylinder wall and'radial constriction is thereby resisted.

27. A piston adapted for reciprocationin the bore of a cylinder, embodying a relatively rigidexial core of relatively small diameter; a relatively rigid radial intermediate its ends, of slightly less diameter than the cylinder'bore, saidcore and Hange forming, in conjunction with the cylinder bore, relatively large annular` spaces intermediate the flange and ends of the core and itermediate the periphery of the core 28. A piston and the cylinder Wall, and a relatively small annular space intermediate the peripheral face of the flange and the cylinder wall; a solid rubber packing sleeve molded on the core, encasing the' core and flange andfilling said annular spaces, whereby axially reinforced throughout its length by the'core and heldy against longitudinal displacement thereon by the Hange; said sleeve constituting the sole packing element be-l tween the piston and cylinder wall and also forming themajor areas of the work ends of the piston, Vthe radial Harige providing a rigid radial backing for the central overlying portion ofthe sleeve and a compression abut-ment for the end portions to resist forces successively exerted by the fluid pressure of the cylinder acting on the work ends of the sleeve. Y

adapted for reciprocation in the bore of a cylinder, comprising a relatively rigid axial core of relatively small diameter;

a relatively rigid radial Hange on the core spaced from the work end thereof,said Hange being of slightly less diameter than that of the cylinder bore; a rubber packing :sleeve molded on the core, overlying the'periphery of the flange and filling the annular space intermediatev said Hange and vthe end of the core. andthe periphery of the core and the cylinder wall, whereby said Hange provides rigid radial backing forl thevoverl'ying portion of the. sleeve and rigidv longitudinal backing therefor on the work stroke of the piston, said 4sleeve having a longitudinally overhanging peripheral portion on the work end of larger diameter than that ofthe cylinorally extending face on der bore when unconfined therein, and a latthe work end mergwhereby said overhanging ends are ra- Hange on said core,

the sleeve is by compression against the radial Hange eX- pand the rearward portion i into pressural contact with the cylinder wall. l

29. A piston having a metallic hub; a solid rubber freely HeXible packing member molded upon and encasing the hub; a radial flange on thel hub intermediate its ends extending into the packing member, centrally of its length, said -Hange being of a diameter slightly less than the diameter of the packing member, to rigidly reinforce 'said-member centrally of its length and leave the portions on either side thereof free to Hex, the-periphery of the packing member being substantially concave and its ends recessed so the peripheral portion overhangs the body portion, the faces of the ends of the packing member having ogee curvatures adjacent the periphery.

30. A piston having a metallic hub; a cylinder engaging rubber packing member on lsaid hub, the peripher of the packing member being substantial y concave and overhanging the body portion at the work end;

the face of the work end having an ogee curvature adjacent the periphery; the outwardly bulged portion of the ogee-.curve posed nearest to and directly, beneath the periphery of the overhanging work end.

3l. Avpiston having a metallic hub; a cylinder engaging rubber packing member encasing said hub; means in connection with the hub, encased by the packing member, to prevent aXial displacement of said member on the being dis- Y hub, the periphery of the packing member Y being substantially concave and the peripheral portion overhanging the body portion at thework end; the face of the work end having an ogee curvature adjacent the periphery.

' 32. A piston having a metallic hub; a cylinder engaging rubber packing member encasing said hub means in connection with the hub, encased bv the packing member, to prevent aXial and lateral displacement of said member on the hub, the periphery of the packing member' beingsmaller-in diameter intermediate its ends than at said ends, the peripheral portion overhanging the body portion at the work end, and the face of the work end havinghan ogee curvature adjacent the periphery. i

c 33. A piston, having a metallic hub; a rubber cylinder engaging packing member encasing the hun, the periphery of the packing member being smallerin diameter intermediate its ends than at said ends, so said ends will be constricted in circumference when the pisto pres ntl unbroken contact withthe wall of a cylin r when placed therein; and the face ,of the vvork end having an ogee curvatureadjacent the periphery.

therein; and means in connection With the core providing relatively rigid longitudinal backing for the sleeve, permitting radial ilexing of the overhanging ends, whereby the internal luid pressure of the cylinder, on the work stroke of the piston, will force the-overhanging ends into close peripheral contant with the cylinder Wall and by compression against the longitudinal backlng means expand the intermediate portion of the sleeve 20 into close der Wall. i

In Witness that I claim the foregoing lI have hereunto subscribed my nameA this 31 day of Dec., 1924. i

peripheral Contact' with the cylin- JOHN W. MCQUAID. 

